Introduction: Continuously Rotating Solar Motor
Who is not dreaming of making an object that is continuously in motion? Day and night, summer and winter, cloudy sky and in-house light conditions. This pulse motor runs for a very long time, maybe longer than my lifespan.
Light on the solar panel charges a super capacitor via a low-dropout regulator. A Hall sensor detects the rotor magnet. The pulse passes the pulse shaper, comperator and driver IC (3 in one) and activates the pulse coil.
The two spheres are from an embroidery frame. Magnetic bearings are used to reduce the friction of the rotor shaft to a minimum. A mattres needle with a very sharp point is doing the job. The rotor is made from a styrofoam globe and has 5 magnets placed around the middle.
I use very small SMD (nanopower) IC's with a few hundred nano ampére current consumption. The circuit is a design of myself, very sensitive and stable. It has a wide voltage supply range from 1.7V till 3 volt.
- IC: SM351LT Hall sensor
- IC: TS881 comperator
- IC: XC 6206 LDO
- Solar panel: 5.5V 90mA, all panels between 3.5V and 5.5V will do.
- SuperCap: 50 Farad, 3V, all between 10F and 50F will do.
- Coil from a 220V relay, 12.8k Ohm
Embroidery frame 12 cm diameter, mattres needle and styrofoam globe.
Neodymium magnets 1cm diameter by 2mm high for rotor and bearing
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Step 1: Video
Step 2: Electronic Circuit
I build the circuit from scratch. This are the conditions:
- All the IC's have to be ultra low power
- SM351LT Hall Sensor, current 360nA, voltage 1.65V - 5.5V.
- TS881 comperator, current 210nA, voltage 0.85V - 5.5V
- XC6206 LDO, current 1uA, voltage input 6V max, output 3V
- Equivalent IC: Comperator LMC7215, Hall DRV5032
- Pulse coil from a 220V AC relay with 12kOhm resistance
By turning the potmeter Rv, the pulsewidth can be regulated between 20 and 60 msec. The photo from the oscilloscope shows the output pulse from the Hall sensor in yellow. The red shape is the output from the TS881 activating the coil. The TS881 triggers on the down going edge and makes a nice regular 50msec pulse on the output. This pulseshaper is very energy efficient, because less pulse time is less current.
In the scheme you see also the pinout of the SMD chips. Take care they are very small and soldering is a skill. Photo's show how I did the job. The TS881 is soldered on a DIL8 socket, that worked out well.
Step 3: Some Details
Step 4: The Construction
A 12cm diameter embroidery frame is the basis of this construction. Within turns a 6cm styrofoam globe as the rotor of the pulse motor. One ring is connected with a heavy bottom piece. On this rest the electronic circuit. Only the hall sensor and the pulse coil are leading to the globe section via electric wires.
Within the second ring the bearings are connected on aluminium strips. On one side is the magnet and at the otherside is the glass plate connected with second glue. The lower strip connects also the hall sensor and the pulse coil with a thick copper wire. They can be positioned to get the best timing for the pulse coil. That is a very precise job.
The rotor shaft is a very sharp mattress needle standing on the glassplate and pulled in position by the magnet. The upper part of the shaft does't touch the glass, it turns free and is pulled up by the magnet. This makes the friction very low. Photo's and video show how all is made in detail.
Step 5: Conclusion
What I want to show is a very efficient pulse motor driven by a small and stable nanopower circuit. The power supply by a small solar panel and a supercap as energy storage have proven that this pulse motor can run for a very long time. It is a challenge to go batteryless. Ultra low power circuits and supercaps makes it possible.
This is a research and fun project. Many skills are coming together to get this working. The best part is playing with electro-magnetic, magnetic and gravity force fields. You can only see their phenomena. Good tools and measuring instruments makes it more easy to solve on-going problems on the way to continuity. Finally, I don't claim anything like perpetuum mobile, eternal run, free energy, etc. but this project comes quite near to that.